N-Doped Nonalternant Molecular Bowl/Saddle Hybrids

Herein, we report the straightforward synthesis and properties of N-doped molecular bowl/saddle hybrids with nonalternant topologies via successive palladium-catalyzed annulations. Structural evolutions from twisted, bowl-shaped to bowl/saddle-hybridized structures are involved during the core-expansion process, as confirmed by X-ray crystallographic analyses. Notably, this resultant bowl/saddle-hybridized molecular carbon shows unique molecular dynamics, as revealed by ¹H NMR, chiral HPLC analyses and theoretical calculations. These molecules exhibit interesting photophysical properties, including moderate fluorescence quantum yields and narrowband emissions. Steady-state and transient spectroscopy reveal the different photophysical properties in these molecular bowl and bowl/saddle hybrids. Moreover, the molecular bowl/saddle hybrid exhibits the shape-adaptive character, and allow for multiple bindings with fullerene guests in a stoichiometry ratio of 1:3, which is seldomly observed in most nonplanar molecular carbons. This study not only presents an efficient strategy to construct a new family of N-doped nonalternant molecular bowl/saddle hybrids, but also provides insights into molecular design of topological nanocarbons with potential applications of chiral materials and organic electronics.